The present invention relates, in general, to electrical power metering apparatus and, specifically, to electrical watthour meters and watthour meter sockets.
In the electric utility industry, plug-in, socket-type watthour meters are commonly employed to measure electric power consumption at a residential or commercial building establishment. A socket is mounted on a wall of the residence or building and contains terminals which are connected to electric line and electric load conductors. The terminals are also connected to internal conductors within the socket which extend to jaw contacts positioned to receive the blade terminals of a plug-on watthour meter to complete an electric circuit through the watthour meter between the line and load terminals and the conductors.
One type of meter socket has a ring-type cover which includes an outwardly projecting, annular mounting flange surrounding an opening in the cover through which the blade terminals of a watthour meter extend. The mounting flange is sized to mate with a complementary formed mounting flange on the bottom of the watthour meter.
In high power applications, current levels exceed the ratings of commonly available watthour meters. In these applications, current transformers are placed around the incoming line conductors and connected to watthour meter receiving jaw contacts to enable watthour meters to measure load current and provide a scaled power measurement.
A special socket, referred to as a K-series socket, is shown in FIGS. 1–4. The socket is designed for single or three-phase power and is designed to carry current up to 400 amps. Rigid bus bar terminals are provided in the upper portion of the socket for receiving the line conductors. Similar plate-like bus bar terminals are mounted at the bottom of the socket for receiving the load conductors. A single mounting fastener, such as a bolt, is provided on each load bus bar for receiving a rigid load bus bar extending from a watthour meter which is mountable in the socket. Similar mounting fasteners, such as bolts, are mounted in a first row on the upper line power bus bars for receiving a separate line bus bar extending from a watthour meter.
As also shown in FIGS. 1–4, shorting bus bars extend between each line bus bar and the corresponding load bus bar provide a bypass power connection from the power distribution line network to the individual load distribution network in a building.
As is evident from FIGS. 1–4, a specially designed watthour meter with rigid bus bars is necessary for mounting in the K-series socket in both the power measurement and non-power measurement positions.
When it is necessary to remove the meter from the socket for replacement or repair, jumpers are connected between at least each line bus bar and each associated line bypass bus bar to prevent the loss of electrical service when the meter is removed from the socket. The nuts on the bus bar and bypass bus bar studs are loosened and a slotted conductive plate which is mounted on one end of an electrically insulated rod shaped handle is inserted between the nuts and bus bars before the nuts are re-tightened. The nuts connecting the meter bus bars to the line and load bus bar studs are removed to enable the meter to be removed from the socket and a new meter installed. After the new meter is installed, the jumper is removed by a reverse operation from that described above. This is a time consuming process.
The installation and removal of the jumpers poses a safety hazzard to the utility service person since the meter is installed and removed from the socket under live power conditions. The service person must use a nut driver or socket wrench to loosen and tighten the stud nuts in order to install and remove the jumper. Accidental dropping of the wrench or nut driver can cause the wrench or nut driver to fall into the socket and possibly short across the bus bars creating a hazardous short which could damage the socket and cause injury to the service person.
It would be desirable to provide a terminal jumper which can be installed in and removed from the socket in less time and under safer conditions than previous socket jumpers.